This application relates generally to gas turbine engines and, more particularly, to gas turbine engine rotor assemblies.
A gas turbine engine typically includes a multi-stage axial compressor, a combustor, and a turbine. Airflow entering the compressor is compressed and directed to the combustor where it is mixed with fuel and ignited, producing hot combustion gases used to drive the turbine. To control the heat transfer induced by the hot combustion gases entering the turbine, typically cooling air is channeled through a turbine cooling circuit and used to cool the turbine.
Compressor bleed air is often used as a source of cooling air for the turbine cooling circuit and is also used to purge cavities defined within the engine. More specifically, maintaining sufficient cooling air and purging of air cavities within the gas turbine engine may be critical to proper engine performance and component longevity. However, extracting cooling air from the compressor may affect overall gas turbine engine performance. Balanced with the need to adequately cool components is a desire to maintain high levels of operating efficiency, and as such, generally, because the temperature of air flowing through the compressor increases at each stage of the compressor, utilizing cooling air from the lowest allowable compressor stage results in a lower engine performance decrement as a result of such cooling air extraction. However, within such engines, during at least some engine power settings, the compressor system may fail to provide purge air at a sufficient pressure, and as such hot gases may be still be ingested into the cavities. Over time, continued exposure to such temperature excursions may limit the useful life of components adjacent to the cavities.